Waste-heat boiler system



J. E. BELL.

WASTE HEAT BOILER SYSTEM.

APPLICATION FILED OCT. 19, 1920. 1,408,972. fi w r- 7, 1922.

v 2 SHEETSSHEET 1.

mvamon MW. a may 5 M ATTORNEY 1. E; BELL. WASTE HEAT BOILER SYSTEM.

' APPLICATION FILED 00119, 1920.

Patented Mar. 7, 1922.

.INVENTOR ameg BY 7 W QD ATTORNEY UNITED STATES PATENT Joan E BELL, on NEW YORK, N. Y.

WASTE-HEAT BdILER SYSTEM.

Specification of Letters Patent.

Patented Mar. 7, 1922.

Application filed October 19, 1920. Serial No. 417,899.

To all a; ham it may concern:

Be it known that I,'J0HN E. BELL, citizen of the United States, and resident of the city of New York, in the county of Kings and State of New York, have invented certain new and useful Improvements in Waste-Heat Boiler Systems, of which the following is a specification.

My present invention consists in an improved waste heat boiler system especially devised for use in connection with a cement plant comprising a plurality of kilns, to recover the available heat in the kiln gases. To make such a waste heat system commercially feasible and desirable it is ob- 'l viously necessary that the waste heat apparatus should not prevent eflicient operation of the cement plant itself, and that its contruction and operating costs must be low enough to permit an adequate monetary return on the waste heat plant invested since the possibilit of such a return is the primary reason, or the waste heat installation. 1

' In the practical operation of such a waste heat plant it is essential that the dust laden heating gases from the cement kilns be moved through the intertube spaces of the boilers and economizers at relatively high speeds ,to obtain efficient heat absorption with boilers and economizers' relatively small and hence inexpensive in first cost, and to avoid dust 'deposits on the heat absorbing surfaces of the boilers and economizers, materially reducing the boiler and economizer heat absorption capacity. The maintenance of, the necessary high speed of gas flow through the boilers and economizers requires a high draft suction at the heating outlets from the boiler housings and in practice the necessary draft cannot be obtained by stack suction alone,but requires the use of exhaust fans driven by steam turbines or electric motors and consuming substantial amounts of power in their operation. The cost ofthe exhaust fans and their driving motors is a substantial item in the first cost of the waste heat installation, and the cost of the power required for their operation, and of the repairs necessary for their maintenance in operation are main items inthe cost of operation of the waste heat plant.

Practical considerations require that a cement plant waste heat boiler installation shall ordinarily comprise a plurality of.

sary to cut one exhauster out of service for cleaning, inspection or repairs, it has also been necessary to cut the boiler in the same unit out of service, or vice-versa and the general object of the present invention is to improve a plant of the character specified by making provisions whereby the various boilers and the various exhausters each forms a separate unit which can be cut out of service while all the remainingv units are eft in operation. By doing this I make possible a-substantial reduction in the initial cost of the plant and a substantial reduction in the cost of the plant maintenance and operation as is hereinafter fully explained.

The various features of novelty which characterize my invention are pointed out with particularity in the claim annexed to and forming a part of this specification.

For a better understanding of the invention, however, and. its advantages, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described a preferred embodiment of my invention.

Of the drawlngs; I

Fig. 1 is a diagrammatic plan view of a waste heat plant;

Fig. 2 is a sectional elevation taken on the line 2-2 of Fig. 1 ;and

Fig. 3 is a diagrammatic plan view illustratinga modification of the plan shown in Fig.

In the drawings, and referring first to the construction shown in Figs. 1 and 2, I have illustrated the use of my invention in a waste heat boiler system for handling the hot gases from a battery of rotary cement kiln, but which may be connected thereto when the corresponding flue connection D is closed to permit the operation of the kiln at that time without waste heat recovery. Associated with the flue D is a battery of waste heat boilers F of which there are four in the particular plant of ordinary capacity shown, though it is to be understood that such a plant sometimes comprises more and sometimes less than four boilers. The housin of each boiler F is connected to the.flue%) by an individual connection D which may be closed when necessary by a damper or valve inserted in the guidewayor valve seat E. The bottom walls of the passages D and D and of the flue D are sloped as shown in Fig. 2 so that deposited dust tends to pass through the outlets D into the screw conveyor DA located beneath and parallel to flue D.

As shown the boilers F are water tube boilers and each is provided with baflies G, Gr and Gr transverse to the water tubes F, for causing the gases to traverse the in ter tube space four times in passing from the boiler housing inlet D to the outlet of the boiler housing before entering to the chamber in the boiler housing containing the ec'onomizer H which is located beneath the water tubes at the front end of the boiler. ,In so far as above described the waste heat boiler system contains nothing claimed in this specification as novel with me, though it does embody features of construction and arrangement claimed in patent applications previously filed by me.

In the construction shown each economizer chamber is normall connected at its bottom through a port Il to aflue J running pilrall'el to the flue D. A damper or valve is provided for closing each port H when necessary. Each damper H may be put into and out of place through an open ing F provided for the purpose in the side of the corresponding boilen housing. Assoclated with the flue J are a plurality of motor driven exhaust fans -L each driven by a suitable motor LA whit-h ordinarily is a steam turbine. Each exhauster discharges 1nto a corresponding stack M as shown in Figs. 1 and 2 and each is shown as connected to the flue J By a corresponding pair ,of inlet passages which are normally open but may be closed when necessar or able by the dampers or valves L.

narily, and as shown, there are as many desirexhausters L as there are boilers F. Dust dropping out of the flue gases in the asses of the boiler between the baflie walls] and G and G and G collects in pockets '1 havlng sloping bottom walls which converge to outlet passages 1 controlled by dampers or valves I which may be manipulated by operating extensions I extending to the exterior of the boiler housing. The assages I open-into the flue J and the atter is provided at its bottom with dust receiving pockets J open at their tops to. the flue J and open at their bottoms through outlets J mto the casmg of a screw conveyor K more than the volume of gases passed by it 180 Ordiwhich extends parallel to the flue J and is connected at its dischar e end to a dust receiver P, and damper The dust handling mechanism just referred to comp-rises various n'ovel characteristics and advantages which however need not be described herein, as they form no part of the present invention and are set forth and claimed in a companion application filed of even date herewith.

In the normal intended operation of the apparatus shown in 1 and 2, the passages D, D H and are all open, and each exhauster L creates the necessary draft for passing to the corresponding stack M the quantity of gases passing through a single boiler F and economizer H. Practically the work performed by each exhauster then is that required to .move the proper amount of heatmg gases through the passages of a single bo1ler andleconomizer at the proper speed. The draft uired at the outlet of the kiln proper is neg igible in amount in comparision with that r uired to producethe necessary velocity 0 flow through the restricted lpasages of the boiler and economizer, and in practice the stacks M rovide a proximately the amount of dra t require at the delivery ends of the kilns. I

Because of the high draft required and the severe operating conditions, it is frequently necessary to cut the diflerent boilers and exhausters out of operation for purposes of inspection, cleaning and repairs. By closin the appropriate assage D and H;

or J 4 1n the'apparatus s own in Figs. 1 and 2, any one boiler or anyone exhauster may be cut out of service while the-other units of the plant remain in operation. In addition to the obvious convenience and flexibility of operation of an arrangement permitting the operation of any desired number of boiler units and exhauster units at one time, there is a special advantage of prime-economic importance in the capacity for rendering one boiler inoperative while all the exhausters remain in operation, and for rendering one exhauster inoperative while all the boilers remain in operation.-

is maintained is simply to increase the work 7 normally required from each of the other exhausters by 331}%, since each exhauster remaining in operation then passes one thirdwith all four exhausters in operation, and the pressure differential between the stacks M and the flue J is unchanged. The-effect of simultaneously iutting outof operation one boiler and one exhauster without reducing the cement kiln and boiler output is to increase the work performed by each of the three exhausters remaining in service, not 33;}%, but about 139%, for when a boiler is cut out of operation the quantity of gases which must be moved through each of the boilers remaining in service is not only increased 4,, but the draft differential between the fines D and J must be nearly doubled. The draft differential required to move the gases through the restricted passages in the boiler housing varies in approximate proportion to the s uare of the velocity of flow of the gases. Io increase the gas flow through the boiler by one third therefore requires the draft differential to be in- The energy required for the operation of each of the three exhausters then in operation is 10 2277 'L. requirement of each exhauster.

If one boiler is out of service while the other three boilers and the four exhausters continue to handle the same total amount of gases as before, it becomes necessary to increased to of its normal value.

xtimes the normal energy crease the draft differential between the fiues D and J to 9 of its normal value, but

cut an exhauster out of service much more frequently than a boiler. The maintenance of full cement plant and boiler plant outputs with one boiler out of service requires the use of an exhauster capable of operation with a load approximately 78% in excess of the normal maximum exhauster load. Whilethe effect of cutting out both a boiler and an exhauster is to make it necessary to provide an exhauster large enough to carry a load approximately 139% in excess day of October, A. D.

of its normal full exhauster load when all boilers and exhausters are in service. The advantage of this reduction in maximum exhauster capacity required is especially important when the exhausters are driven by steam turbines as is usual, for in that case the reduction in exhauster capacity made possible by the use of the invention, not only substantially reduces the size and hence the first cost of the exhausters and the maximum steam consumption required for their operation, but substantially increases the efliciency of the plant in normal operation with all of the boilers and exhausters in service, since, as is well known to those skilled in the art, the efliciency of a turbo exhauster is markedly lower at small loads than at higher loads.

Instead of providing each motor driven exhauster L with a corresponding stack M, each exhauster L may discharge throu h an individual outlet into a common flue connected to a common stack T as shown in Fi 3. When this construction is employed, a damper or valve is provided as indicated at L for closing communication between each exhauster and the flue S.

While in accordance with the rovisions of the statutes I have illustrate and described the best form of apparatus embodying my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention as set forth in the appended claim and that certain features of my invention may sometimes be used to advantage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

A waste heat boiler system for cement plants comprising, in combination, a flue receivin hot gases from a plurality of cement k1 us, a second flue, a plurality of separate waste heat boilers connected between said flues, a plurality of motor driven exhausters separately connected to said second flue, and provisions for separately closing the flue connections to the various b011- ers and exhausters to permit any boiler or exhauster in the plant to be cut out of service while the other boilers and exhausters remain in service.

Signed at New York, in the county of New York and State of New York, this 16th 1920. JOHN E. BELL. 

